Insulation sheet is typically provided in a secondary battery, which can effectively prevent side walls and bottom surface of the naked battery core from contacting with housing of the secondary battery.
In the related art, the secondary battery is typically formed as a connection structure by buckling a top bracket on each long side of the head cover, respectively, and protruding a lower plastic of an electrode pole downward from a short side of the head cover to be parallel and level with the top bracket. During assembly, the naked battery core is first assembled with the above connection structure by connecting with a top connection sheet. Then, the naked battery core insulation sheet goes upward gradually from the bottom of the naked battery core to wrap a side wall of the naked battery core, and finally, is hot-melt connected with the top bracket and the lower plastic.
In such a connection structure, however, both the lower plastic and the top bracket need to protrude downward a certain distance along the head cover, and therefore, when assembled, a certain height space needs to be occupied, which is undesired for simplifying the assembling process and improving the capacity of the battery.